The present invention relates to cryosurgical instruments and more particularly to a cryosurgical instrument which may be used with a number of different, interchangeable spray and closed end cryotips.
Cryosurgery can be used in treating a number of different medical conditions. For example, cryosurgery can be used in the treatment of hemorrhoids, in removal of undesirable growths or skin tumors, in the course of ophthalmic operations and for many other similar and dissimilar surgical procedures. In some of these procedures, a spray cryotip is used to spray cold refrigerant liquid directly onto the tissue to be necrosed. Contact with the liquid and evaporation of the liquid from the tissue lowers the tissue temperature sufficiently to provide necrosis. In other procedures, a closed end cryotip is used. In such a cryotip, a refrigerant fluid, which may be either gas or liquid, is delivered to an expansion chamber within the cryotip. The cryotip is formed from a material having a high thermal conductivity. The expanding refrigerant cools the cryotip which is placed in direct contact with the tissue to be treated to bring about necrosis of that tissue.
The amount of tissue to be treated and the accessability of that tissue varies with the cryosurgical procedure to be performed. For that reason, special purpose cryotips have been developed for particular procedures.
Cryosurgical instruments have also been developed which may be used with interchangeable closed end cryotips. The cryotips used with such instruments have basically the same internal structure, differing from one another only in the external configuration.
However, because the construction of spray cryotips is dissimilar to the construction of closed end cryotips, those instruments which could accept interchangeable closed end cryotips could not accept spray cryotips.
Since the surgeon might need both types of cryotips in his practice, he either had to buy separate cryosurgical instruments for use with two different types of tips or avoid performing certain types of cryosurgical procedures.
U.S. Pat. No. 3,651,813 discloses a cryosurgical instrument in which a delivery tube is permanently connected to a container of liquified gas coolant. The container is attached directly to a handle having a channel which may be left open to relieve gas pressure in the container when the instrument is not in use. When the instrument is to be used, this channel is closed to allow gas pressure in the container to build up at ambient temperatures so as to force liquid coolant through a dip tube, actually an extension of the delivery tube. The instrument can be used either as a spray-type instrument or, by threading a cap onto the end of the delivery tube, as a closed end type instrument. When used in the closed end mode, effluent refrigerant is exhausted through an effluent channel terminating at the handle of the instrument.
Since the delivery tube is an integral part of the instrument, its dimensions cannot be changed to allow the instrument to perform different cryosurgical procedures as efficiently as a cryosurgical instrument having a tip with a delivery tube and an outer casing specifically designed for that procedure. Moreover, the effluent refrigerant is exhausted relatively near the tissue being treated. This is generally undesirable since the refrigerant is not always as sterile as might be desired. Finally, since the refrigerant pressure is relatively low, the refrigerant delivery rate may not be adequate for certain types of cryosurgical procedures.